1. Field of the Invention
The present invention relates to a fluorescent lamp.
2. Description of the Related Art
Conventionally, during the last period of the life of a fluorescent lamp, when all electron emitting substances filled into an electrode filament coil dissipate, a cathode drop voltage rises and power consumption in an electrode increases. Thus, the temperature in the vicinity of an electrode sealing portion on the end of a light-emitting tube is excessively increased, and heat generation may occur. As a method for preventing such a rise in temperature or excessive heat generation from occurring, the following has been known: A thermal fuse or the like is provided in the vicinity of the end of the light-emitting tube. The excessive heat generated in the end of the light-emitting tube melts and cuts off this thermal fuse, so that a lighting circuit is interrupted (see JP 2-192650A and JP 4-61740A).
In recent years, a compact one-base-type fluorescent lamp with a small tube diameter has been developed and commercially expanded as an energy-saving light source to be substituted for light bulbs or the like. When such a fluorescent lamp is lit by a high-frequency electronic circuit, a preheating current may continue to flow through the electrode filament coil depending on the electronic circuit system, even if the lamp cannot light up because of the dissipation of all the electron emitting substances in the last period of lamp life.
In this case, the glass temperature of the electrode sealing portion rises excessively because an arc discharge or the like is generated between the electrode lead wires holding the electrode filament coil, thereby causing a breakdown. Thus, the preheating current flows in the glass between the electrode lead wires to increase the temperature of the electrode sealing portion excessively.
For one-base-type fluorescent lamps, a rise in temperature of the electrode sealing portion is especially remarkable, and thus a base made of a resin material may be deformed by heat. In order to prevent such a rise in temperature, the high-frequency electronic circuit is generally provided with a so-called protection circuit for detecting the dissipation of all the electron emitting substances in the electrode and stopping the electronic circuit operation. However, even if such a protection circuit is provided, the failure of the protection circuit, though it rarely occurs, may cause the above-mentioned base deformation or the like. As a method for preventing such a rise in temperature of the electrode sealing portion that leads to the base deformation or the like, the following has been known: A thermal protection element, such as a thermal fuse or the like is provided in the base so as to be connected in series with an outer electrode lead wire (see JP 10-188906A and JP 11-111231A).
FIG. 33 shows an example of a configuration of a one-base-type fluorescent lamp according to the conventional techniques. In a light-emitting tube 137 (with an outer diameter of about 17 mm) having a pair of electrodes therein, four straight glass tubes 138, 139, 140, and 141 are joined to form a discharge path therein. A base 142 is provided on the end of the tube of the light-emitting tube 137. Base contact pin terminals 145, 151, 152, and 153 are provided on the base 142 and connected to electrode lead wires 144, 148, 149, and 150 drawn from the light-emitting tube 137, respectively. In the base 142, a thermal protection element 143 that acts as a thermal fuse is connected to the electrode lead wire 144 drawn from the light-emitting tube 137 and the base contact pin terminal 145 by caulking.
In addition to the four straight tubes type described above, two, six, and eight straight tubes types conventionally have been known as the one-base-type fluorescent lamps. Among these types, e.g., in the one-base-type fluorescent lamp of four straight tubes type provided with the thermal protection element (hereinafter referred to as a thermal fuse) 143, as shown in FIG. 33, the base 142 generally includes a light-emitting tube holding member 146 and a base body 147 that mainly are made of a resin material, as shown in FIG. 34.
In the manufacturing processes for this type of fluorescent lamp, first, the ends of the four tubes of the light-emitting tube 137 are inserted into circular holes of the light-emitting tube holding member 146, and then fixed with an adhesive of a silicone resin or the like. Then, one end of the thermal fuse 143 and one end of the electrode lead wire 144 are connected. Then, the light-emitting tube holding member 146 and the base body 147 are fixed. Finally, the remaining three electrode lead wires 148, 149, and 150 and the other end of the thermal fuse 143 are connected to the base contact pin terminals 151, 152, 153, and 145 attached to the base body 147 by soldering or caulking. Also, in the two, six, and eight straight tubes types (with an outer diameter of the light-emitting tube of about 12 mm or about 17 mm), the base includes two parts that are basically the same as in the above four straight tubes type. In addition, the base assembly process is basically the same.
On the other hand, as an example of the kind of high wattage lamp of the two straight tubes type (with an outer diameter of the light-emitting tube of about 20 mm, and the electric power of 28 W. 36 W. 55 W, or 96 W), a lamp with the structure shown in FIGS. 35, 36, and 37 is provided. FIG. 35 is a sectional front view of a base portion, and FIGS. 36 and 37 are plan views thereof. In this lamp, a base 154 is provided with a base body 155, two covers 156, 157 shown in FIG. 37, and two thermal fuses 158, 159 shown in FIG. 36. FIG. 36 is a plan view of a base not including the covers 156, 157.
In the manufacturing processes for this type of fluorescent lamp, the thermal fuses 158, 159 are accommodated in the predetermined positions in the base body 155. Then, one side lead wire of each of the thermal fuses 158, 159 is inserted into respective base contact pin terminals 160, 161. At the same time, electrode lead wires 166, 167 drawn from a light-emitting tube 164 are inserted into base contact pin terminals 163, 162, respectively. Then, the light-emitting tube 164 is fixed in the base body 155 with a silicon adhesive or the like. The electrode lead wires 166, 167, and the one side lead wire of each of the thermal fuses 158, 159 that have been inserted into the base contact pin terminals 160, 161, 162, and 163, then are connected to the base contact pin terminals 160, 161, 162, and 163, respectively, by caulking. Furthermore, electrode lead wires 165, 168 and the other side lead wire of each of the thermal fuses 158, 159 are connected by caulking terminals 169 made of metal, and then the connected portions are inserted into the base body 155 to which the two covers 156, 157 are attached.
In a conventional fluorescent lamp without the thermal fuse, e.g., when a base is attached, electrode lead wires are arranged straight so as to be led to base contact pin terminals. Thus, when the end of a light-emitting tube is inserted into the base, the electrode lead wires spontaneously are led to and inserted into the corresponding base contact pin terminals, respectively. Therefore, for the conventional fluorescent lamp without the thermal fuse, the processes from the manufacture of a fluorescent lamp to base assembly generally are performed by a series of automatic manufacturing equipment or the like, so that mass production easily is achieved, and thus the manufacturing cost of lamps can be lowered.
However, for a conventional fluorescent lamp with the thermal fuse described above, in its manufacturing processes, it is difficult to connect the lead wires of the thermal fuse to an electrode lead wire of the light-emitting tube and a base contact pin terminal by automation, and thus these connections have to be established by manual operation. As a result, the manufacturing cost of lamps increases.
In a time of saving energy, to supply safe and popularly priced one-base-type fluorescent lamps to the market as an energy-saving light source to be substituted for light bulbs, reduction of the manufacturing cost of lamps provided with the thermal fuse is a task to be achieved.
Therefore, with the foregoing in mind, it is an object of the present invention to provide a fluorescent lamp that easily can achieve the mass production of lamps by a series of automatic manufacturing equipment or the like while simplifying the manufacturing processes of a fluorescent lamp provided with a thermal fuse and facilitating the operation thereof, and that can reduce the manufacturing cost significantly. It is another object of the present invention to provide a fluorescent lamp with excellent safety that ensures that the thermal fuse provided therein is melted and cut off as the temperature rises excessively in the last period of lamp life.
A fluorescent lamp of the present invention includes a light-emitting tube having a pair of electrodes therein, a base for fixing the light-emitting tube, and a base contact pin terminal supported by the base with one end thereof projecting from the base. The base contact pin terminal and an electrode lead wire drawn from the light-emitting tube are electrically connected. The base is provided with a first power-conducting member including the base contact pin terminal having a lead plate, a connecting terminal having a lead plate and connected to the electrode lead wire, and a thermal protection element connected to the lead plate of the base contact pin terminal and the lead plate of the connecting terminal.
This allows the manufacturing processes of a fluorescent lamp to be reduced and simplified in comparison with the conventional techniques. In addition, the mass production of lamps by a series of automatic manufacturing equipment or the like easily can be achieved, and thus the manufacturing cost required for producing fluorescent lamps can be reduced significantly. Furthermore, as the temperature rises excessively in the last period of lamp life, the thermal fuse provided in a lamp can be melted and cut off reliably, so that fluorescent lamps with excellent safety can be obtained.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.